Portable devices, such as mobile phones, tablet devices, digital cameras, and other types of computing and electronic devices may be designed with a touchscreen for user input with a stylus or touch contact. Typically, a user can contact the touchscreen of a device to access the functionality of the device. For example, touchscreen contact may be used to open, close, and use applications, or to modify device settings. In general, two types of styluses may be used to provide input to a touchscreen—a passive stylus and an active stylus.
The data captured by a conventional touchscreen that is used with a passive stylus generally only indicates whether the stylus is contacting the touchscreen and, if so, the x-y position of the stylus on the touchscreen.
In contrast, an active stylus is a powered input device that can, among other functions, measure contact pressure between the stylus and the touchscreen, and provide that information to the device to help distinguish between contact and hovering. However, to measure and transmit this data, as well as to produce and transmit other data, an active stylus requires a battery or other power source inside the stylus.
The use of a stylus in touchscreen scenarios enables information to be captured at a higher level of precision than, for example, input provided by a finger. This is because the contact footprint of a stylus is typically much smaller than the contact footprint of a finger. Higher input precision, however, requires finer precision in the sensing circuitry. Yet, the higher input precision that comes with sensing circuitry that is finer in its sensing precision is often unnecessary when the touch input is received from a finger, whose contact footprint is much larger than the contact footprint of the stylus. This unnecessary input sensing precision can, and often does, lead to wasteful power consumption by the computing device. That is, if the touch input is received from a finger, then using the finer sensing precision that is more fitting for stylus input is not necessary.